Design, fabrication, and testing of silicon microgimbals for super-compact rigid disk drives

This paper documents results related to design optimization, fabrication process refinement, and micron-level static/dynamic testing of silicon micromachined microgimbals that have applications in super-compact computer disk drives as well as many other engineering applications of microstructures and microactuators requiring significant out-of-plane motions. The objective of the optimization effort is to increase the in-plane to out-of-plane stiffness ratio in order to maximize compliance and servo bandwidth and to increase the displacement to strain ratio to maximize the shock resistance of the microgimbals, while that of the process modification effort is to simplify in order to reduce manufacturing cost. The testing effort is to characterize both the static and dynamic performance using precision instrumentation in order to compare various prototype designs

Magnetics in Smart Grid

This journal issue contain selected papers from the Asia-Pacific Data Storage Conference (APDSC'13)A revolution in power transmission and distribution, driven by environmental and economic considerations, is occurring all over the world. This revolution is spearheaded by the development of the smart grid. The smart grid is bringing profound change to both the power systems and many related industries. This paper reviews the development of the smart grid and its correlation with magnetics, including electromagnetic compatibility issue, magnetic-field-based measurement/monitoring, and magnetic energy storage/conversion. The challenge to the field of magnetics and the usage of the cutting edge magnetics technology in the development of the smart grid are discussed. This paper enables researchers in the magnetics community to be acquainted with the progress in the smart grid and inspires innovative applications of state-of-the-art magnetics technologies in the smart grid.published_or_final_versio

Fundamental efforts for improving the sensitivity of magnetic resonance force microscopy

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011."July 2011." Cataloged from PDF version of thesis.Includes bibliographical references (p. 20-24).Introduction: Complete understanding of the mechanisms of biological processes, indispensable for the rational design and testing of therapeutic strategies, can be greatly facilitated by easy and rapid access to macromolecular structures at the atomic resolution. As of 2011, a general method for rapid rendering of macromolecular and cellular structures with atomic resolution represents both a major challenge and a major need in science. Such a method would prove all the more valuable to understanding the conformational complexities of protein misfolding diseases and amyloid formation phenomena , caused by complex networks of structural transition reactions linking the monomeric, oligomeric, and polymorphic fibrillar forms of disease-causing proteins, the structures of which have only been rigorously characterized in a small number of cases. To date, the majority of protein and RNA structures known have been solved by either X-ray crystallography or by NMR spectroscopy. Many requirements on the sample prevent these methods from being generally applicable to biological specimens. First, since X-ray crystallography and NMR spectroscopy are techniques based on assessing the average properties of a macroscopic sample, a high degree of sample heterogeneity undermines their ability to solve structures. Second, X-ray crystallography requires the sample protein to form ordered crystals. However, the procedure for crystallizing proteins remains a daunting trial-and-error process and important proteins like membrane proteins are impossible to crystallize in their native forms. Recent advances in solid state NMR (ssNMR) spectroscopy have made it possible to study membrane proteins, but the technique is still limited by protein size and by the need for order, at least at the local level. For these reasons, the structural studies of macromolecule that contain high degrees of conformational heterogeneity and that are large in size have remained challenging, rare, and largely tackled, with difficulty, by computational approaches.by Ye Tao.S.M

Engineering Magnetoresistance in MnxGe1−x System for Magnetic Sensor Application

In 2007, a Nobel Prize is awarded to Dr. Albert Fert and Peter Grünberg for their contribution in giant magnetoresistance (GMR) effect. The magnetic head based on GMR effect has significantly increased the storage density in the hard disk drive (HDD) and brought the coming of the digital age. Besides, the rapid development of GMR sensor has opened a wide and promising range of applications, including the aspects in automobile, traffic monitor, biomedicine, and space, etc. As continuously extending the market, it needs GMR sensor with much lower cost, smaller size, higher sensitivity, and compatibility with the CMOS technology. In light of that, we give a review about the recent progress of the MR effect in MnxGe1−x system, which refers to the material growth and magnetic and MR property. Through engineering the MnxGe1−x structure, it could realize the transition from negative to positive MR, geometric-enhanced giant MR, and electric-field controlled MR. The fact of well-designed MR effect and high compatibility with Si technology brings a high potential and advantage for fabricating MnxGe1−x-based MR sensors, which could be widely used in magnetic head and biomedical sensors, among others, with the superiority of much lower manufacturing cost, lower power dissipation, higher integration density, and higher sensitivity

The Smartphone Brain Scanner: A Portable Real-Time Neuroimaging System

Combining low cost wireless EEG sensors with smartphones offers novel opportunities for mobile brain imaging in an everyday context. We present a framework for building multi-platform, portable EEG applications with real-time 3D source reconstruction. The system - Smartphone Brain Scanner - combines an off-the-shelf neuroheadset or EEG cap with a smartphone or tablet, and as such represents the first fully mobile system for real-time 3D EEG imaging. We discuss the benefits and challenges of a fully portable system, including technical limitations as well as real-time reconstruction of 3D images of brain activity. We present examples of the brain activity captured in a simple experiment involving imagined finger tapping, showing that the acquired signal in a relevant brain region is similar to that obtained with standard EEG lab equipment. Although the quality of the signal in a mobile solution using a off-the-shelf consumer neuroheadset is lower compared to that obtained using high density standard EEG equipment, we propose that mobile application development may offset the disadvantages and provide completely new opportunities for neuroimaging in natural settings

NONINVASIVE MULTIMODAL DIFFUSE OPTICAL IMAGING OF VULNERABLE TISSUE HEMODYNAMICS

Measurement of tissue hemodynamics provides vital information for the assessment of tissue viability. This thesis reports three noninvasive near-infrared diffuse optical systems for spectroscopic measurements and tomographic imaging of tissue hemodynamics in vulnerable tissues with the goal of disease diagnosis and treatment monitoring. A hybrid near-infrared spectroscopy/diffuse correlation spectroscopy (NIRS/DCS) instrument with a contact fiber-optic probe was developed and utilized for simultaneous and continuous monitoring of blood flow (BF), blood oxygenation, and oxidative metabolism in exercising gastrocnemius. Results measured by the hybrid NIRS/DCS instrument in 37 subjects (mean age: 67 ± 6) indicated that vitamin D supplement plus aerobic training improved muscle metabolic function in older population. To reduce the interference and potential infection risk on vulnerable tissues caused by the contact measurement, a noncontact diffuse correlation spectroscopy/tomography (ncDCS/ncDCT) system was then developed. The ncDCS/ncDCT system employed optical lenses to project limited numbers of sources and detectors on the tissue surface. A motor-driven noncontact probe scanned over a region of interest to collect boundary data for three dimensional (3D) tomographic imaging of blood flow distribution. The ncDCS was tested for BF measurements in mastectomy skin flaps. Nineteen (19) patients underwent mastectomy and implant-based breast reconstruction were measured before and immediately after mastectomy. The BF index after mastectomy in each patient was normalized to its baseline value before surgery to get relative BF (rBF). Since rBF values in the patients with necrosis (n = 4) were significantly lower than those without necrosis (n = 15), rBF levels can be used to predict mastectomy skin flap necrosis. The ncDCT was tested for 3D imaging of BF distributions in chronic wounds of 5 patients. Spatial variations in BF contrasts over the wounded tissues were observed, indicating the capability of ncDCT in detecting tissue hemodynamic heterogeneities. To improve temporal/spatial resolution and avoid motion artifacts due to a long mechanical scanning of ncDCT, an electron-multiplying charge-coupled device based noncontact speckle contrast diffuse correlation tomography (scDCT) was developed. Validation of scDCT was done by imaging both high and low BF contrasts in tissue-like phantoms and human forearms. In a wound imaging study using scDCT, significant lower BF values were observed in the burned areas/volumes compared to surrounding normal tissues in two patients with burn. One limitation in this study was the potential influence of other unknown tissue optical properties such as tissue absorption coefficient (µa) on BF measurements. A new algorithm was then developed to extract both µa and BF using light intensities and speckle contrasts measured by scDCT at multiple source-detector distances. The new algorithm was validated using tissue-like liquid phantoms with varied values of µa and BF index. In-vivo validation and application of the innovative scDCT technique with the new algorithm is the subject of future work

Spatially resolved surface dissipation over metal and dielectric substrates

We report spatially resolved measurements of static and fluctuating electric fields over conductive (Au) and non-conductive (SiO2) surfaces. Using an ultrasensitive `nanoladder' cantilever probe to scan over these surfaces at distances of a few tens of nanometers, we record changes in the probe resonance frequency and damping that we associate with static and fluctuating fields, respectively. We find that the two quantities are spatially correlated and of similar magnitude for the two materials. We quantitatively describe the observed effects on the basis of trapped surface charges and dielectric fluctuations in an adsorbate layer. Our results provide direct, spatial evidence for surface dissipation in adsorbates that affects nanomechanical sensors, trapped ions, superconducting resonators, and color centers in diamond

Progress on the ultrasonic testing and laser thermography techniques for NDT of tokamak plasma-facing components

During manufacturing and operation, different kinds of defects, e.g., delamination or surface cracks, may be generated in the plasma-facing components (PFCs) of a Tokamak device. To ensure the safety of the PFCs, various kinds of nondestructive testing (NDT) techniques are needed for different defect and failure mode. This paper gives a review of the recently developed ultrasonic testing (UT) and laser thermography methods for inspection of the delamination and surface cracks in PFCs. For monoblock W/Cu PFCs of divertor, the bonding quality at both W-Cu and Cu-CuCrZr interfaces was qualified by using UT with a focus probe during manufacturing. A noncontact, coupling-free and flexible ultrasonic scanning testing system with use of an electromagnetic acoustic transducer and a robotic inspection manipulator was introduced then for the in-vessel inspection of delamination defect in first wall (FW). A laser infrared thermography testing method is highlighted for the on-line inspection of delamination defect in FW through the vacuum vessel window of the Tokamak reactor. Finally, a new laser spot thermography method using laser spot array source was described for the online inspection of the surface cracks in FW